Instrument for measuring near point of convergence and/or near point of accommodation

ABSTRACT

An instrument for measuring near point of convergence (NPC) and/or near point of accommodation (NPA) is disclosed herein. The instrument includes an instrument housing, at least one visual target viewable by the subject; a distance measuring device configured to emit one or more output signals that are representative of a distance between a measurement reference point of the instrument and a body surface of the subject spaced apart from the measurement reference point of the instrument; and a processing device operatively coupled to the distance measuring device, the processing device configured to receive the one or more output signals that are output by the distance measuring device and to calculate the distance between the measurement reference point of the instrument and the body surface of the subject using the one or more output signals. In one or more embodiments, the instrument further includes a camera and a light source.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation-in-part of U.S. Nonprovisional patent applicationSer. No. 14/509,928, entitled “Instrument for Measuring Near Point ofConvergence and/or Near Point of Accommodation”, filed on Oct. 8, 2014,and further claims the benefit of U.S. Provisional Patent ApplicationNo. 61/888,615, entitled “Instrument for Measuring Near Point ofConvergence and Near Point of Accommodation”, filed on Oct. 9, 2013, thedisclosure of each of which is hereby incorporated by reference as ifset forth in their entirety herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable.

INCORPORATION BY REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISK

Not Applicable.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention generally relates to an instrument for vision testing.More particularly, the invention relates to an instrument for measuringnear point of convergence (NPC) and near point of accommodation (NPA).

2. Background

Near point of convergence (NPC) is measured by bringing an object closeto a user's eyes, and measuring the distance from the eyes at which theuser begins to see double. Near point of accommodation (NPA) is measuredby bringing an object close to a user's eyes, and measuring the distancefrom the eyes at which the object appears blurry to the user. Presently,devices for measuring NPC and NPA rely on manual measurements, recordingand the use of crude tools. As such, an improved instrument formeasuring NPC and NPA is needed.

BRIEF SUMMARY OF EMBODIMENTS OF THE INVENTION

Accordingly, the present invention is directed to an instrument formeasuring near point of convergence (NPC) and/or near point ofaccommodation (NPA) that substantially obviates one or more problemsresulting from the limitations and deficiencies of the related art.

In accordance with one or more embodiments of the present invention,there is provided an instrument for measuring near point of convergence(NPC) and/or near point of accommodation (NPA). The instrument includesan instrument housing, the instrument housing including a front surfaceand a rear surface disposed opposite to the front surface, theinstrument housing having a length and a width, the width of theinstrument housing being less than the length of the instrument housingso as to enable a user of the instrument to view the eyes of a subjectwhile the subject is being tested using the instrument; at least onevisual target disposed on or in the front surface of the instrumenthousing, the at least one visual target viewable by the subject when thesubject is facing the front surface of the instrument; a distancemeasuring device disposed on or in the front surface of the instrumenthousing, the distance measuring device configured to emit one or moreoutput signals that are representative of a distance between ameasurement reference point of the instrument and a body surface of thesubject spaced apart from the measurement reference point of theinstrument; and a processing device disposed within the instrumenthousing, the processing device operatively coupled to the distancemeasuring device, the processing device configured to receive the one ormore output signals that are output by the distance measuring device andto calculate the distance between the measurement reference point of theinstrument and the body surface of the subject spaced apart from themeasurement reference point of the instrument using the one or moreoutput signals.

In a further embodiment of the present invention, a ratio of the lengthof the instrument housing to the width of the instrument housing isbetween approximately 2 to 1 and approximately 12 to 1.

In yet a further embodiment, a ratio of the length of the instrumenthousing to the width of the instrument housing is between approximately5 to 1 and approximately 10 to 1.

In still a further embodiment, the at least one visual target comprisesone or more optotypes and/or one or more letters of a recognizedalphabet that are capable of being identified by the subject.

In yet a further embodiment, the instrument further comprises a cameradisposed on or in the front surface of the instrument housing, thecamera configured to capture a pupil image of the subject while thesubject is being tested using the instrument. In this furtherembodiment, the processing device is further operatively coupled to thecamera, the processing device being configured to determine a pupil sizeof the subject from the pupil image of the subject captured by thecamera.

In still a further embodiment, the instrument further comprises a lightsource disposed on or in the front surface of the instrument housing,the light source configured to stimulate a pupil response from thesubject while the pupil image of the subject is being captured by thecamera.

In yet a further embodiment, the light source is in the form of alight-emitting diode.

In still a further embodiment, the distance measuring device comprises arange detector with a transmitter portion for emitting an ultrasonic orinfrared pulse and a receiver portion for receiving the ultrasonic orinfrared pulse after it is reflected off the body portion of thesubject.

In yet a further embodiment, the processing device is in the form of amicroprocessor.

In still a further embodiment, the instrument further comprises at leastone of a wireless data interface or a wired data interface operativelycoupled to the processing device, the wireless data interface or thewired data interface configured to operatively couple the instrument toa remote electronic device so that data stored in the instrument iscapable of being transmitted to the remote electronic device.

In yet a further embodiment, the instrument further comprises a visualdisplay device operatively coupled to the processing device, the visualdisplay device configured to display the distance calculated by theprocessing device to the user of the instrument for at least one visiontest measurement parameter of the subject.

In still a further embodiment, the visual display device is configuredto display the distance calculated by the processing device to the userof the instrument for a plurality of vision test measurement parameters,the plurality of vision test measurement parameters selected from thegroup consisting of near point of convergence (NPC), near point ofconvergence recovery (NPCr), near point of accommodation (NPA), nearpoint of accommodation recovery (NPAr), and combinations thereof.

In yet a further embodiment, the instrument further comprises one ormore user input devices configured to enable a user to perform one ormore operations using the instrument.

In still a further embodiment, the one or more user input devicescomprise a plurality of user input buttons, a first of the plurality ofuser input buttons being configured to control the power of theinstrument, a second of the plurality of user input buttons beingconfigured to initiate a measurement of the distance by the distancemeasurement device, and a third of the plurality of user input buttonsbeing configured to initiate a transfer of data from the instrument to aremote electronic device.

In accordance with one or more other embodiments of the presentinvention, there is provided an instrument for measuring near point ofconvergence (NPC) and/or near point of accommodation (NPA). Theinstrument includes an instrument housing, the instrument housingincluding a front surface and a rear surface disposed opposite to thefront surface; at least one visual target disposed on or in the frontsurface of the instrument housing, the at least one visual targetviewable by the subject when the subject is facing the front surface ofthe instrument; a distance measuring device disposed on or in the frontsurface of the instrument housing, the distance measuring deviceconfigured to emit one or more output signals that are representative ofa distance between a measurement reference point of the instrument and abody surface of the subject spaced apart from the measurement referencepoint of the instrument; a camera disposed on or in the front surface ofthe instrument housing, the camera configured to capture a pupil imageof the subject while the subject is being tested using the instrument;and a processing device disposed within the instrument housing, theprocessing device operatively coupled to the distance measuring deviceand the camera, the processing device configured to receive the one ormore output signals that are output by the distance measuring device andto calculate the distance between the measurement reference point of theinstrument and the body surface of the subject spaced apart from themeasurement reference point of the instrument using the one or moreoutput signals, the processing device further configured to determine apupil size of the subject from the pupil image of the subject capturedby the camera.

In a further embodiment of the present invention, the instrument furthercomprises a light source disposed on or in the front surface of theinstrument housing, the light source configured to stimulate a pupilresponse from the subject while the pupil image of the subject is beingcaptured by the camera.

In yet a further embodiment, the instrument housing has a length and awidth, the width of the instrument housing being substantially less thanthe length of the instrument housing so as to enable a user of theinstrument to view the eyes of a subject while the subject is beingtested using the instrument without the instrument housing obstructingthe eyes of the subject.

In still a further embodiment, a ratio of the length of the instrumenthousing to the width of the instrument housing is between approximately2 to 1 and approximately 12 to 1.

In accordance with yet one or more other embodiments of the presentinvention, there is provided a method for measuring near point ofconvergence (NPC) and/or near point of accommodation (NPA) of a subject.The method comprising the steps of: (i) providing an instrument; (ii)displaying, by using the instrument, the at least one visual target tothe subject so that the subject is able maintain his or her gaze on theat least one visual target while the user of the instrument observes theeyes of the subject; and (iii) determining and recording, by using theinstrument, either a diplopia distance which corresponds to a point atwhich the subject sees a double image of the visual target or anaccommodation threshold distance at which the subject sees a blurryimage of the visual target precluding an accurate identification of thevisual target. The instrument includes an instrument housing, theinstrument housing including a front surface and a rear surface disposedopposite to the front surface, the instrument housing having a lengthand a width, the width of the instrument housing being less than thelength of the instrument housing so as to enable a user of theinstrument to view the eyes of the subject while the subject is beingtested using the instrument; at least one visual target disposed on orin the front surface of the instrument housing, the at least one visualtarget viewable by the subject when the subject is facing the frontsurface of the instrument; a distance measuring device disposed on or inthe front surface of the instrument housing, the distance measuringdevice configured to emit one or more output signals that arerepresentative of a distance between a measurement reference point ofthe instrument and a body surface of the subject spaced apart from themeasurement reference point of the instrument; and a processing devicedisposed within the instrument housing, the processing deviceoperatively coupled to the distance measuring device, the processingdevice configured to receive the one or more output signals that areoutput by the distance measuring device and to calculate the distancebetween the measurement reference point of the instrument and the bodysurface of the subject spaced apart from the measurement reference pointof the instrument using the one or more output signals.

In a further embodiment of the present invention, the instrument furthercomprises a camera disposed on or in the front surface of the instrumenthousing, the camera configured to capture a pupil image of the subjectwhile the subject is being tested using the instrument, and the camerabeing operatively coupled to the processing device. In this furtherembodiment, the method further comprises the step of determining, byusing the processing device, a pupil size of the subject from the pupilimage of the subject captured by the camera while the subject is beingtested using the instrument.

In accordance with still one or more other embodiments of the presentinvention, there is provided a method for measuring near point ofconvergence (NPC) and/or near point of accommodation (NPA) of a subject.The method comprising the steps of: (i) providing an instrument; (ii)positioning the instrument at an initial distance from the front of thehead of the subject; (iii) displaying, by using the instrument, the atleast one visual target to the subject so that the subject is ablemaintain his or her gaze on the at least one visual target; (iv)gradually advancing the instrument towards the front of the head of thesubject while the distance between the surface of the instrument and thefront of the head of the subject is calculated by the processing deviceof the instrument; (v) stopping the advancement of the instrumenttowards the front of the head of the subject when a point is reached atwhich the subject either sees a double image of the visual target or thesubject sees a blurry image of the visual target precluding an accurateidentification of the visual target; and (vi) determining and recording,by using the instrument, either a diplopia distance which corresponds tothe point at which the subject sees the double image of the visualtarget or an accommodation threshold distance at which the subject seesthe blurry image of the visual target precluding the accurateidentification of the visual target. The instrument includes at leastone visual target disposed on or in the instrument, the at least onevisual target viewable by a subject that is facing the instrument; adistance measuring device, the distance measuring device configured toemit one or more output signals that are representative of a distancebetween a surface of the instrument and a front of a head of a subjectspaced apart from the surface of the instrument; and a processing deviceoperatively coupled to the distance measuring device, the processingdevice configured to receive the one or more output signals that areoutput by the distance measuring device and to calculate the distancebetween the surface of the instrument and the front of the head of thesubject spaced apart from the surface of the instrument using the one ormore output signals;

In a further embodiment of the present invention, the method furthercomprises performing an additional test, which includes the additionalsteps of: (vii) gradually advancing the instrument towards the front ofthe head of the subject until a first point is reached at which thesubject sees a double image of the visual target; (viii) stopping theadvancement of the instrument upon reaching the first point, and thensubsequently gradually moving the instrument away from the front of thehead of the subject until a second point is reached at which the subjectno longer sees the double image of the visual target; and (ix)determining and recording, by using the instrument, a recovery distancewhich corresponds to the point at which the subject no longer sees thedouble image of the visual target.

It is to be understood that the foregoing general description and thefollowing detailed description of the present invention are merelyexemplary and explanatory in nature. As such, the foregoing generaldescription and the following detailed description of the inventionshould not be construed to limit the scope of the appended claims in anysense.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The invention will now be described, by way of example, with referenceto the accompanying drawings, in which:

FIG. 1 is an exploded view of an instrument for measuring near point ofconvergence and near point of accommodation, according to one embodimentof the invention;

FIG. 2A is a top view of the instrument of FIG. 1;

FIG. 2B is a left side view of the instrument of FIG. 1;

FIG. 2C is a front view of the instrument of FIG. 1;

FIG. 2D is a right side view of the instrument of FIG. 1;

FIG. 2E is a rear view of the instrument of FIG. 1;

FIG. 3A is a rear view of the back plate of the instrument of FIG. 1;

FIG. 3B is a side view of the back plate of the instrument of FIG. 1;

FIG. 3C is a perspective view of the back plate of the instrument ofFIG. 1;

FIG. 4A is a front view of the face plate of the instrument of FIG. 1;

FIG. 4B is a side view of the face plate of the instrument of FIG. 1;

FIG. 4C is a perspective view of the face plate of the instrument ofFIG. 1;

FIG. 5 is a schematic diagram of another instrument for measuring nearpoint of convergence and near point of accommodation, according to analternative embodiment of the invention;

FIG. 6 is a front perspective view of yet another instrument formeasuring near point of convergence and near point of accommodation,according to another alternative embodiment of the invention;

FIG. 7 is a rear perspective view of the instrument of FIG. 6;

FIG. 8 is a front perspective view of still another instrument formeasuring near point of convergence and near point of accommodation,according to yet another alternative embodiment of the invention;

FIG. 9 is a rear perspective view of the instrument of FIG. 8; and

FIG. 10 is a schematic block diagram of the primary electricalcomponents of the instruments illustrated in FIGS. 6-7 and 8-9,according to an embodiment of the invention.

Throughout the figures, the same parts are always denoted using the samereference characters so that, as a general rule, they will only bedescribed once.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In one or more embodiments, an instrument suitable for measuring NPC andNPA is provided. The illustrative instrument described herein includes ahousing which carries a variety of electronics. The electronics includea range detector for measuring the distance between the instrument andthe subject. The electronics also include a variety of visual targets,such as LEDs, which a subject looks at during the tests. The electronicsalso include a computer chip which stores data and controls the variousattached systems. The illustrative instrument described herein issuitable for administering tests for NPC and NPA.

In accordance with an illustrative embodiment, an instrument 20 fordigitally measuring both near point of convergence (NPC) and near pointof accommodation (NPA) is shown in FIGS. 1-4C. The instrument includes abody formed from a front face plate 1 and a back face plate 7 (see e.g.,FIG. 1). The front face plate 1 (see FIGS. 4A-4C) and the back faceplate 7 (see FIGS. 3A-3C) together define a cavity which houses avariety of electronics, including a screen 8, a range detector 2, asystem chip 9, a battery 10, and various targets and switches. As anexample of one such switch, the instrument 20 may comprise a powerswitch 13 (e.g., a medium rocker switch—see e.g., FIG. 2B) for turningthe device “on” and “off”. These elements carried within the instrumentare described in greater detail below. In one exemplary embodiment, thebattery 10 may comprise a 9-volt battery.

In another embodiment, rather than using the front face plate 1 and theback face plate 7 illustrated in the figures for the housing of theinstrument 20, the instrument 20 may comprise an alternative electronicsenclosure with split sides and internal supports for accommodating aprinted circuit board (PCB) mounted therein. The alternative electronicsenclosure may comprise a battery compartment to accommodate a 9-voltbattery, and may be fabricated from a suitable polymeric material orplastic, such as acrylonitrile butadiene styrene (ABS). In an exemplaryembodiment, the alternative electronics enclosure may have an overalllength of approximately 120 millimeters (mm), an overall width ofapproximately 60 millimeters (mm), and overall height of approximately25 millimeters (mm). Although, it is to be understood that the inventionis in no way limited to these particular dimensions. Rather, theinvention may be practiced using any other suitable dimensions withoutdeparting from the spirit and scope of the appended claims.

The instrument 20 utilizes ultrasonic and/or infrared signals to measurethe proximity of the instrument 20 to the bridge of the nose and/orforehead of a subject as the instrument 20 is moved to a given positionrelative the subject. The instrument 20 includes a range detector 2which is suitable for emitting an ultrasonic or infrared pulse whichbounces off the structure of the face or forehead of the subject andreturns to a receiver portion of the range detector 2. The round-triptravel time of the pulse from range detector 2 is used to calculate thedistance between the instrument 20 and the face or forehead of thesubject. In one or more embodiments, the range detector 2 may comprisean ultrasonic range detector module with an emitter portion and receiverportion.

In one or more embodiments, the round-trip travel time of the pulse fromrange detector 2 may be used to calculate the distance (D) between thefront surface of the instrument 20 and the face or forehead of thesubject in the following manner:

$\begin{matrix}{D = \frac{t*v_{s}}{2}} & (1)\end{matrix}$where:

t=round-trip travel time of the pulse from the range detector emitter tothe detector

v_(s)=velocity of sound (340 meters per second).

In an exemplary embodiment, the ultrasonic range detector module with anemitter portion and receiver portion may have a 5-volt supply voltage, atrigger pulse input (e.g., 10 microsecond transistor-transistor logic(TTL) pulse), an echo pulse output, a maximum range of approximatelyfour (4) meters, a minimum range of approximately two (2) centimeters,and a measuring angle of approximately 15 degrees. In the exemplaryembodiment, the emitter or transmitter portion of the ultrasonic rangedetector module may emit an 8 cycle burst of ultrasound at 40 kHz andraise its echo.

The instrument 20 includes a front face plate 1 having several targetsthereon. These targets are preferably lights, such as LEDs, at which thesubject can fix his gaze during a test. The instrument 20 is suitablefor performing multiple tests on a subject. The first test utilizes afirst target 3, which may be a tricolor light-emitting diode (LED). Inone exemplary embodiment, the tricolor light-emitting diode (LED) maycomprise a 10 mm RGB diffused LED. To perform the first test, theinstrument 20 is placed a suitable distance from the front of thesubject's head, such that the instrument 20 is beyond the distance wherethe subject will see double (at this distance, the user only sees asingle LED 3). The instrument 20 is then moved toward the subject'shead, and as the instrument 20 is moved the instrument measures thedistance between the instrument and the subject's head. As this distancedecreases, the color of the first target 3 proceeds through a series ofcolor changes, for instance, the first target may start red, change toyellow, and finally change to green as it moves closer to the subject'shead. The purpose of the color change of the first target 3 is to makethe first target 3 more interesting, keeping the subject's attentionduring the test. Alternatively, the instrument may be configured suchthat the first target remains a constant color throughout the test. Whenthe instrument 20 reaches a point where the user indicates that they seedouble (e.g., the user sees two LEDs 3), a button 14 is pressed which isconnected to a piezo element 11 (see FIG. 1), which in turn is connectedto system chip 9 which is suitable for recording, storing, andprocessing information from the various systems in the instrument 20. Inone exemplary embodiment, the button 14 may comprise a momentarypushbutton switch (e.g., 12 mm square momentary pushbutton switch—seee.g., FIG. 2D). The range detector 2 and the button 14 are both inelectrical communication with the chip 9 which instructs the rangedetector 2 to measure the distance between the instrument 20 and thesubject, and records and stores this information on the chip 9. The chip9 is also connected to a display 8 which displays the recorded distance.In one or more exemplary embodiments, the chip 9 of the instrument 20may comprise a central control board or microcontroller with a centralprocessing unit (CPU) or microprocessor, flash program memory, datamemory, EEPROM data memory, and a plurality of input/output (I/O) ports.In an exemplary embodiment, the microcontroller may have a 20 MHz clockspeed, 4K flash program memory, and an operating voltage range of 2.0Vto 5.5V.

In an alternative exemplary embodiment, the microcontroller may have a16 MHz clock speed, 32 k flash memory, an input voltage of 7-12V,fourteen (14) digital input/output (I/O) pins (6 PWM outputs), and six(6) analog inputs.

The instrument 20 will also include a second target 5 which includesthree single-colored LED's, one red, one green or blue, and one clearincluded on the front face 1 of the instrument 20. The second target 5is suitable for use when administering a second test, administered to asubject wearing red/green or blue glasses (also known as anaglyphglasses), which second test can be used to determine if the subject issuppressing vision in an eye. Anaglyph glasses typically include a redlens over the right eye and a green or blue lens over the left eye. Ared lens will block green light, and the green lens will block redlight. If the red LED cannot be seen by the subject, this is anindication that vision in the subject's right eye (the eye associatedwith the green lens of the glasses) is suppressed. If the green or blueLED cannot be seen, this is an indication that the vision in thesubject's left eye (the eye associated with the red lens of the glasses)is suppressed. The clear LED is viewable by both eyes when the subjectwears the glasses, and is used for either testing or training purposes,similar to the Worth four dot test.

The instrument 20 includes a speaker 24 which is in electricalcommunication and is controlled by the chip 9. The speaker 24 emits atone which varies in pitch as the instrument approaches the subject'shead. The chip 9 is suitable for translating the distance measured bythe range detector 2 into a particular pitch emitted by the speaker 24.In this way, during administration of the test, the instrument 20 beginsat a position spaced away from the subject's head, and as the instrumentis advanced toward the head the pitch of the tone increases from low tohigh.

The instrument 20 includes a display screen 8 on the back face plate 7(see e.g., FIG. 2E). As the various tests are administered, the screen 8displays the distance of the instrument 20 to the subject (such as ininches or centimeters). In an exemplary embodiment, the display screen 8may comprise a serial liquid crystal display (LCD) module. The button 14is included on the instrument 20. When the button 14 is pressed, theinstrument 20 will electronically store the distance between theinstrument 20 and the subject's head at that point in time as measuredby the range detector 2. During the administration of a test, thesubject will be instructed to indicate when they notice a particularoccurrence relative to one or more of the targets, such as when theyexperience double vision or suppression. Alternatively, the button 14may be pressed when the person performing the test notices either thatthe subject's eyes converge, or that the subject's eyes stop converging.

The instrument 20 includes a wireless transmitter which is suitable forwirelessly transmitting data stored in the instrument to another device,such as a computer, a smartphone, or other suitable device. In oneinstance, the wireless transmitter is integrated with the chip 9, in anycase, the wireless transmitter is in electrical communication with, andis controlled by, the chip 9. The wireless transmitter utilizes one ormore wireless communication technologies which are common in the market,such as WiFi, Bluetooth and/or near field communication (NFC). Theinstrument 20 also includes a port (not shown) which is suitable forestablishing a wired connection between the chip 9 and a computer,smartphone or other suitable device. Further, the instrument 20 alsoincludes a compact removable memory chip (not shown) as are known, suchas a removable flash memory storage device, for storing data collectedon the chip 9 and transferring the data to a computer, smartphone orother suitable device.

The instrument 20 described herein is also suitable for measuring nearpoint of accommodation (NPA). The front panel 1 of the instrument 20includes a third target (see e.g., FIG. 5, Snellen box). The thirdtarget includes a series of symbols, such as the types of symbols whichare generally included on an eye chart (such as a variation of a Snellenchart, Tumbling E chart, Landolt C chart, or other similar eye chart).During a test for NPA, the instrument 20 is positioned at a point spacedfrom the subject's head, with the front panel of the instrument 20facing the subject. The subject views the front face 1 of the instrument20 with the eye being tested, while the untested eye is covered with anoccluding device. The instrument 20 is then moved slowly toward thesubject until the subject reports that the third target is too blurry toread, the distance from the subject's head to the instrument is thenrecorded by pressing the button 14 on the instrument 20. The test isthen repeated for the subject's other eye. Finally, the test is repeateda third time, but without either eye obstructed by the occluding device.The results of each iteration of the test are stored on the chip 9 andoptionally displayed on the screen 8.

The instrument 20 is also suitable for measuring the recovery point ofthe subject's eyes. The recovery point is measured by having the subjectfocus on the first target 3 (a single LED) with both eyes as theinstrument is advanced toward the subject's head. The subject indicateswhen the first target appears as two LEDs—when the subject is seeingdouble. The instrument 20 is then slowly moved away from the subjectuntil the subject indicates that the first target appears as a singleLED—the subject is no longer seeing double. This point where the subjectis no longer seeing double is known as the recovery point. This point ismeasured by the range detector 2 when the user presses the button 14 andrecorded and stored on the chip 9 of the instrument 20, and optionallydisplayed on the screen 8.

The instrument 20 includes one or more input devices. The input devicesare suitable for collecting responses from a user. One such input deviceis the button 14, described herein. Another input device is one or morebuttons 12 which may be positioned on the front face 1 or on a sidethereof. The one or more buttons 12 allow a user to toggle between thedifferent tests which may be administered by the instrument 20 (seee.g., FIGS. 2A and 2C). In one instance, a separate button 12 isprovided to correspond with each of the tests administered by theinstrument 20. In an exemplary embodiment, the instrument 20 maycomprise three (3) buttons 12 in the form of three (3) single pole,double throw (SPDT) mini power switches, e.g., one for each test thatmay be administered. However, it is to be understood that, in otherembodiments, four or more buttons 12 may be provided in order toaccommodate four or more tests that are administered using theinstrument 20 (as described below). In each case, the input devices arein electrical communication with the chip 9, which chip 9 in turn is inelectrical communication with the various components of the instrument20 and activates those components as described herein when a particulartest is selected by the user using the input devices. Other inputdevices which are known are suitable for use with the instrument,including a touch screen, a microphone for receiving voice commands, aport for connecting an external keyboard or other input device, wirelesscontrol via a smartphone or other device, or any other known inputdevice as is known and would be suitable for providing input signals tothe chip 9 to initiate a given test.

With reference to the schematic diagram 100 of FIG. 5, anotherillustrative embodiment of the instrument 20 will be described. As shownin this figure, the front face or subject side 102 of the instrumentcomprises the emitter 104 and the receiver 106 of the ultrasonic rangedetector module, a first target 108 (i.e., similar to target 3 describedabove), a plurality of second targets 110 (i.e., similar to secondtargets 5 described above), and a third target 112 comprising a seriesof symbols, such as Snellen chart symbols (i.e., see third targetdiscussion above). In an exemplary embodiment, the series of symbols ofthe third target may comprise a string of letters, such as “E B T C M BL A” and “N G O V M P L E”, which the subject is asked to identifyduring the test. As diagrammatically indicated by the arrows 114 in FIG.5, the front face 102 of the instrument is visible to the subject 116during the vision testing of him or her. Also, as diagrammaticallyrepresented by the downwardly directed arrow in FIG. 5, the components104, 106, 108, 110, 112 that are disposed on the front face 102 of theinstrument are all operatively coupled (i.e., electrically connected) tothe microcontroller 118 of the instrument (refer to discussion ofmicrocontroller above). Referring again to FIG. 5, it can be seen thatthe back face or tester side 122 of the instrument comprises the displayscreen 124 (i.e., similar to display 8 described above) and anarrangement of buttons 126 that are used to select and control thedifferent modes of operation and tests. As diagrammatically indicated bythe arrow 128 in FIG. 5, the display screen 124 and the arrangement ofbuttons 126 on the back face of the instrument are also operativelycoupled (i.e., electrically connected) to the microcontroller 118 of theinstrument. As shown in FIG. 5, the arrangement of buttons 126 maycomprise five (5) or more individuals buttons (e.g., in someembodiments, the instrument 20 may six (6) buttons in lieu of five (5)buttons). The buttons in the arrangement of buttons 126 may be used forcontrolling any or all of the following functions of the instrument: (i)mode/test selection, (ii) intensity control of the targets (i.e.,controlling the brightness of the light emitting devices), (iii)measuring and/or recording the distance between the instrument and theface or forehead of the subject, (iv) activating and deactivating thepower of the instrument (i.e., the main power switch), (v) activatingand deactivating the sound delivered through the speaker of theinstrument, and (vi) activating the Worth 4 dot test.

Now, with reference to FIGS. 6 and 7, yet another illustrativeembodiment of the instrument 200 will be described. As shown in thesefigures, the instrument 200 is similar in many respects to the precedingembodiments of the instrument 20 described above. In particular, likethe instrument 20 described above, the instrument 200 generallycomprises an instrument housing 202, a plurality of visual targets 208on a front surface 204 of the instrument housing 202, a distancemeasuring device or transducer 206 on the front surface 204 of theinstrument housing 202, and a processing device 230 disposed within theinstrument housing 202. As shown in FIGS. 6 and 7, the instrumenthousing 202 has a length L, a width W, and a depth D. In theillustrative embodiment, the width W of the instrument housing 202 issubstantially less than the length L of the instrument housing 202 so asto enable a user of the instrument 200 to view the eyes of a subjectwhile the subject is being tested using the instrument 200 (i.e., theinstrument housing 202 does not obstruct the eyes of the subject so thatthe user of the instrument 200 is able to view the eyes of the subjecton both sides of the instrument 200). As shown in the illustrativeembodiment of FIG. 6, the plurality of visual targets 208, which aredisposed on the front surface 204 of the instrument housing 202, are inthe form of a plurality of different letters of the English alphabet(i.e., letters “T U H X D E Z” of the English alphabet). The visualtargets 208 are viewable by the subject when the subject is facing thefront surface 204 of the instrument 200 (i.e., the subject focuses on aselected one of the letters). As described above, the distance measuringdevice or transducer 206 is configured to emit one or more outputsignals that are representative of a distance between a measurementreference point of the instrument 200 (e.g., a point on the outersurface of the distance measuring device 206) and a body surface of thesubject (e.g., the bridge of the nose and/or forehead of the subject)spaced apart from the measurement reference point of the instrument 200.The processing device 230 (e.g., a microprocessor) is operativelycoupled (i.e., electrically connected) to the distance measuring device206, and receives the one or more output signals that are output by thedistance measuring device 206 so that the distance between themeasurement reference point of the instrument 200 and the body surfaceof the subject are able to be calculated using the one or more outputsignals.

In one or more embodiments, in order to ensure that a user of theinstrument 200 (e.g., a clinician or optometrist) is able to see theeyes of a subject while the subject is being tested using the instrument200, the instrument housing 202 may have a length-to-width ratio (L to Wratio) of between approximately 2 to 1 and approximately 12 to 1 (orbetween 2 to 1 and 12 to 1). More preferably, in one or moreembodiments, the instrument housing 202 may have a length-to-width ratio(L to W ratio) of between approximately 5 to 1 and approximately 10 to 1(or between 5 to 1 and 10 to 1). Also, in one or more embodiments, theinstrument housing 202 may have a width of 1.0 inch or less so that thewidth of the instrument housing 202 does not block the view of thesubject's eyes. For example, in the illustrative embodiment, theinstrument housing 202 may have a length-to-width ratio (L to W ratio)of approximately 5 to 1 so that the instrument housing 202 has anelongate geometry that does not prevent the eyes of the subject frombeing viewed by the clinician during the vision test. In an exemplaryembodiment, the instrument housing 202 has a length L of approximately5.0 inches, a width W of approximately 1.0 inch, and a depth D ofapproximately 0.50 inches.

During the use of the instrument 200, the clinician grasps the bottomportion of the instrument 200 in his or her hand (e.g., just below thevisual targets 208), and displaces the instrument 200 back-and-forthrelative to the subject in the manner described above. Thus,advantageously, the elongate geometry of the instrument housing 202 alsoallows the instrument 200 to be easily held by the clinician during thetesting of the subject. During use, the handheld instrument 200 is heldin an upright manner with the distance measuring device 206 beingdisposed at the top of the instrument 200.

Referring again to FIG. 6, the distance measuring device 206 maycomprise an ultrasonic or infrared transducer with an integratedtransmitter and receiver disposed within the circular footprint of thedevice 206. As described above in the preceding embodiments, thedistance measuring device 206 may comprise a range detector with atransmitter portion for emitting an ultrasonic or infrared pulse and areceiver portion for receiving the ultrasonic or infrared pulse after itis reflected off the body portion of the subject.

Next, turning to FIG. 7, similar to that described above for thepreceding embodiments, it can be seen that the instrument 200 furtherincludes a visual display device 212 disposed on the rear surface 210thereof. The visual display device 212 is operatively coupled (i.e.,electrically connected) to the processing device 230, and the visualdisplay device 212 displays a distance calculated by the processingdevice 230 to the user of the instrument 200 for at least one visiontest measurement parameter of the subject. For example, as shown in theillustrative embodiment of FIG. 7, the visual display device 212displays the distances 224 calculated by the processing device 230 tothe user of the instrument 200 for a plurality of vision testmeasurement parameters 214, namely near point of convergence (NPC), nearpoint of convergence recovery (NPCr), near point of accommodation (NPA),near point of accommodation recovery (NPAr). Each of the distances 224listed on the display 212 in FIG. 7 is in centimeters (cm). As such, inthe illustrative embodiment, the near point of convergence (NPC)distance is 6 centimeters, the near point of convergence recovery (NPCr)distance is 11 centimeters, near point of accommodation (NPA) distanceis 9 centimeters, and the near point of accommodation recovery (NPAr)distance is 14 centimeters. In an exemplary embodiment, a label adjacentto the visual display device 212 may be affixed to the rear surface 210of the instrument housing 202 in order to label the vision testmeasurement parameters 214 that are displayed on the visual displaydevice 212. Alternatively, rather than using a label, the names of thevision test measurement parameters 214 may be imprinted on the rearsurface 210 of the instrument housing 202.

With reference again to FIG. 7, similar to the aforedescribedembodiments, it can be seen that the instrument 200 further includes aplurality of user input devices in the form of a plurality of user inputbuttons 216, 218, 220 disposed on the rear surface 210 thereof. Inparticular, as shown in FIG. 7, the plurality of user input buttonscomprise a first button 216 for controlling the power of the instrument200 (i.e., turning the instrument on and off), a second button 218 forinitiating a measurement and/or recordation of the distance by thedistance measurement device 206 (i.e., for measuring, recording, anddisplaying the distance on the display 212), and a third button 220 forinitiating a transfer of data from the instrument 200 to a remoteelectronic device (e.g., to a laptop or smartphone). As shown in theillustrative embodiment of FIG. 7, indicia 222 may be provided aboveeach of the buttons 216, 218, 220 in order to label the functionality ofthe buttons 216, 218, 220. In an exemplary embodiment, labels may beaffixed to the rear surface 210 of the instrument housing 202, aboveeach of the buttons 216, 218, 220, containing the indicia 222.Alternatively, rather than using labels, the button indicia 222 may beimprinted on the rear surface 210 of the instrument housing 202.

Now, with reference to FIGS. 8 and 9, yet another illustrativeembodiment of the instrument 200′ will be described. With reference tothese figures, it can be seen that, in many respects, the illustrativeembodiment of FIGS. 8 and 9 is similar to that of the embodimentdepicted in FIGS. 6 and 7. Moreover, many parts are common to both suchembodiments. For the sake of brevity, the parts that the embodiment ofFIGS. 8 and 9 has in common with the embodiment of FIGS. 6 and 7 willonly be briefly mentioned, if at all, because these components havealready been explained in detail above. Furthermore, in the interest ofclarity, these components will be denoted using the same referencecharacters that were used in the embodiment of FIGS. 6 and 7.

As shown in FIGS. 8 and 9, the instrument 200′ is similar in manyrespects to the instrument 200 described above. In particular, like theinstrument 200 described above, the instrument 200′ generally comprisesan instrument housing 202, a plurality of visual targets 208 disposed ona front surface 204 of the instrument housing 202, a distance measuringdevice or transducer 206 disposed on the front surface 204 of theinstrument housing 202, a visual display device 212 with adjacentlabeling indicia 214 disposed on the rear surface 210 of the instrumenthousing 202, a plurality of user input buttons 216, 218, 220 withlabeling indicia 222 thereabove disposed on the rear surface 210 of theinstrument housing 202, and a processing device 230 disposed within theinstrument housing 202. However, unlike the instrument 200 describedabove, the instrument 200′ further includes a pair of cameras 226 and alight source 228 disposed on the front surface 204 of the instrumenthousing 202 (refer to FIG. 8). The functionality of each of thesecomponents 226, 228 will be described hereinafter.

As depicted in FIG. 8, like the instrument 200 described above, thedistance measuring device 206 is disposed proximate to the upper end ofthe instrument housing 202 on the front surface 204 thereof so that thedistance measurement may be taken using the forehead of the subject.Then, in FIG. 8, it can be seen that the light source 228 is disposedunderneath the distance measuring device 206. The pair of cameras 226 isdisposed below the light source 228 in FIG. 8 so as to be disposed atapproximately the same elevation or height of the subject's eyes. Thefirst one of the cameras 226 captures a pupil image of the subject'sleft eye while the subject is being tested using the instrument 200′,while the second one of the cameras 226 captures a pupil image of thesubject's right eye while the subject is being tested using theinstrument 200′. Each of the cameras 226 is operatively coupled (i.e.,electrically connected) to the processing device 230 disposed within theinstrument housing 202. The processing device 230 determines right andleft pupil sizes of the subject from respective right and left pupilimages of the subject captured by the cameras 226. As shown in FIG. 8,the light source 228 of the instrument 200′ is also disposed on thefront surface 204 of the instrument housing 202 between the distancemeasuring device 206 and the pair of cameras 226. The light source 228stimulates pupil responses from the subject while the pupil images ofthe subject are being captured by the cameras 226. In an exemplaryembodiment, the light source 228 is in the form of a light-emittingdiode.

As illustrated in the block diagram of FIG. 10, the processing device230 (e.g., a microprocessor) may be electrically connected to each ofthe components 206, 212, 216, 218, 220, 226, 228 of the instrument 200,200′ as shown. In particular, as diagrammatically indicated by thearrows in FIG. 10, the distance measuring device 206 may output a signalto the processing device 230 containing the distance measurementinformation, and in turn, the processing device 230 may output thedetermined distance value to the visual display device 212. Also, thepupil image information for the subject may be transferred to theprocessing device 230 from the cameras 226 so that the processing device230 is able to determine the pupil sizes for the subject. In addition,the processing device 230 may control the operation of the light source228 in order to stimulate pupil responses of the subject while the pupilimages are being captured by the cameras 226. Also, as depicted in FIG.10, the power button 216, the distance measurement button 218, and thedata transfer button 220 may each be operatively coupled to theprocessing device 230 so that the buttons 216, 218, 220 are capable ofperforming the functions described above.

Advantageously, the instrument 20, 200, 200′ described herein issuitable for determining any one of the following four (4) measurements:(i) near point of convergence break (NPCb), (ii) near point ofconvergence recovery (NPCr), (iii) near point of accommodation blur(NPAb), and (iv) near point of accommodation recovery (NPAr). Although,it is to be understood that the instrument 20, 200, 200′ is not limitedto these four (4) particular measurements. Rather, it is suitable formaking other eye-related measurements as well.

The near point of convergence break (NPCb) is the point at which thesubject can no longer converge or cross their eyes. This is tested byhaving the subject fixate on a small object or target as it is broughtslowly towards his or her eyes. The subject is instructed keep thetarget single as long as possible, but to report when the targetdoubles. This is confirmed objectively by the tester watching theireyes. At the point where the subject can no longer cross their eyes,they should report two targets and the tester should notice the eye nolonger making the converging eye movements. This is known as the nearpoint of convergence (NPC) or near point of convergence break (NPCb).

The near point of convergence recovery (NPCr) is the point at which theeyes of the subject will regain convergence. This is tested by startinga target closer to the subject than their NPCb, and slowly moving itdirectly away from the eyes until they see one target instead of two.This is known as the recovery point of near point of convergence, or theNPCr.

The near point of accommodation blur (NPAb) is also tested using theinstrument 20, 200, 200′. This is tested by having the subject observe aline of 20/30 or 20/40 size letters (depending on the age of the subjectand the testing protocol), calibrated for a test distance of 40centimeters (cm). The letters are slowly brought toward the subjectuntil they become too blurry to read. This is known as the near point ofaccommodation or near point of accommodation blur (NPAb).

The near point of accommodation recovery (NPAr) is additionally testedusing the instrument 20, 200, 200′. This test is started with the testletters being closer than the NPAb, and pulling it directly away fromthe subject, noting when they can first begin to read the letters. Thisis the recovery point of accommodation, or the NPAr.

The importance of these measurements has been well documented. They areespecially important measurements pre-concussion and post-concussion.They also have been shown to be a key component in the areas of visuallyrelated learning problems and eye strain.

One application of the aforementioned tests is to determine if a subjectis experiencing a concussion. For many subjects, NPC and NPA will differwhen experiencing concussion symptoms, as compared to the NPC and NPA ofthe subject during normal, or unaffected, conditions. The presentinstrument 20, 200, 200′ can be used to measure a NPC and NPA baseline,in other words, to take measurements of NPC and NPA when the subject isnot experiencing concussion symptoms. The instrument 20, 200, 200′ canthen be used after an incident which has the potential to cause aconcussion as one tool to determine if the subject is experiencingconcussion symptoms.

More broadly, the instrument 20, 200, 200′ is suitable for use tomeasure NPC and NPA as needed, and any reference to use for measuringconcussions should not be read as limiting. For instance, measurement ofNPC and NPA can also be used to detect reading problems.

Although the invention has been shown and described with respect to acertain embodiment or embodiments, it is apparent that this inventioncan be embodied in many different forms and that many othermodifications and variations are possible without departing from thespirit and scope of this invention.

Moreover, while exemplary embodiments have been described herein, one ofordinary skill in the art will readily appreciate that the exemplaryembodiments set forth above are merely illustrative in nature and shouldnot be construed as to limit the claims in any manner. Rather, the scopeof the invention is defined only by the appended claims and theirequivalents, and not, by the preceding description.

The invention claimed is:
 1. An instrument for measuring near point ofconvergence (NPC) and/or near point of accommodation (NPA), theinstrument comprising: an instrument housing, the instrument housingincluding a front surface and a rear surface disposed opposite to thefront surface, the instrument housing having a length and a width, thewidth of the instrument housing being less than the length of theinstrument housing so as to enable a user of the instrument to view theeyes of a subject while the subject is being tested using theinstrument; at least one visual target disposed on or in the frontsurface of the instrument housing, the at least one visual targetviewable by the subject when the subject is facing the front surface ofthe instrument; a distance measuring device disposed on or in the frontsurface of the instrument housing, the distance measuring deviceconfigured to emit one or more output signals that are representative ofa distance between a measurement reference point of the instrument and abody surface of the subject spaced apart from the measurement referencepoint of the instrument; a processing device disposed within theinstrument housing, the processing device operatively coupled to thedistance measuring device, the processing device configured to receivethe one or more output signals that are output by the distance measuringdevice and to calculate a plurality of distances between the measurementreference point of the instrument and the body surface of the subjectspaced apart from the measurement reference point of the instrumentusing the one or more output signals; and a visual display deviceoperatively coupled to the processing device, the visual display deviceconfigured to display the plurality of distances calculated by theprocessing device to the user of the instrument for at least two visiontest measurement parameters of the subject, the at least two vision testmeasurement parameters selected from the group consisting of near pointof convergence (NPC), near point of convergence recovery (NPCr), nearpoint of accommodation (NPA), and near point of accommodation recovery(NPAr); wherein the instrument is in the form of a handheld instrument,and the user of the instrument is configured to hold the instrumenthousing during the use of the instrument.
 2. The instrument according toclaim 1, wherein a ratio of the length of the instrument housing to thewidth of the instrument housing is between approximately 2 to 1 andapproximately 12 to
 1. 3. The instrument according to claim 2, wherein aratio of the length of the instrument housing to the width of theinstrument housing is between approximately 5 to 1 and approximately 10to
 1. 4. The instrument according to claim 1, wherein the at least onevisual target comprises one or more optotypes and/or one or more lettersof a recognized alphabet that are capable of being identified by thesubject.
 5. The instrument according to claim 1, further comprising acamera disposed on or in the front surface of the instrument housing,the camera configured to capture a pupil image of the subject while thesubject is being tested using the instrument; and wherein the processingdevice is further operatively coupled to the camera, the processingdevice being configured to determine a pupil size of the subject fromthe pupil image of the subject captured by the camera.
 6. The instrumentaccording to claim 5, further comprising a light source disposed on orin the front surface of the instrument housing, the light sourceconfigured to stimulate a pupil response from the subject while thepupil image of the subject is being captured by the camera.
 7. Theinstrument according to claim 6, wherein the light source is in the formof a light-emitting diode.
 8. The instrument according to claim 1,wherein the distance measuring device comprises a range detector with atransmitter portion for emitting an ultrasonic or infrared pulse and areceiver portion for receiving the ultrasonic or infrared pulse after itis reflected off the body portion of the subject.
 9. The instrumentaccording to claim 1, wherein the processing device is in the form of amicroprocessor.
 10. The instrument according to claim 1, furthercomprising at least one of a wireless data interface or a wired datainterface operatively coupled to the processing device, the wirelessdata interface or the wired data interface configured to operativelycouple the instrument to a remote electronic device so that data storedin the instrument is capable of being transmitted to the remoteelectronic device.
 11. The instrument according to claim 1, furthercomprising one or more user input devices configured to enable a user toperform one or more operations using the instrument.
 12. The instrumentaccording to claim 11, wherein the one or more user input devicescomprise a plurality of user input buttons, a first of the plurality ofuser input buttons being configured to control the power of theinstrument, a second of the plurality of user input buttons beingconfigured to initiate a measurement of the distance by the distancemeasurement device, and a third of the plurality of user input buttonsbeing configured to initiate a transfer of data from the instrument to aremote electronic device.
 13. An instrument for measuring near point ofconvergence (NPC) and/or near point of accommodation (NPA), theinstrument comprising: an instrument housing, the instrument housingincluding a front surface and a rear surface disposed opposite to thefront surface; at least one visual target disposed on or in the frontsurface of the instrument housing, the at least one visual targetviewable by the subject when the subject is facing the front surface ofthe instrument; a distance measuring device disposed on or in the frontsurface of the instrument housing, the distance measuring deviceconfigured to emit one or more output signals that are representative ofa distance between a measurement reference point of the instrument and abody surface of the subject spaced apart from the measurement referencepoint of the instrument; a camera disposed on or in the front surface ofthe instrument housing, the camera configured to capture a pupil imageof the subject while the subject is being tested using the instrument; aprocessing device disposed within the instrument housing, the processingdevice operatively coupled to the distance measuring device and thecamera, the processing device configured to receive the one or moreoutput signals that are output by the distance measuring device and tocalculate a plurality of distances between the measurement referencepoint of the instrument and the body surface of the subject spaced apartfrom the measurement reference point of the instrument using the one ormore output signals, the processing device further configured todetermine a pupil size of the subject from the pupil image of thesubject captured by the camera; and a visual display device operativelycoupled to the processing device, the visual display device configuredto display the plurality of distances calculated by the processingdevice to the user of the instrument for at least two vision testmeasurement parameters of the subject, the at least two vision testmeasurement parameters selected from the group consisting of near pointof convergence (NPC), near point of convergence recovery (NPCr), nearpoint of accommodation (NPA), and near point of accommodation recovery(NPAr); wherein the instrument is in the form of a handheld instrument,and the user of the instrument is configured to hold the instrumenthousing during the use of the instrument.
 14. The instrument accordingto claim 13, further comprising a light source disposed on or in thefront surface of the instrument housing, the light source configured tostimulate a pupil response from the subject while the pupil image of thesubject is being captured by the camera.
 15. The instrument according toclaim 13, wherein the instrument housing has a length and a width, thewidth of the instrument housing being substantially less than the lengthof the instrument housing so as to enable a user of the instrument toview the eyes of a subject while the subject is being tested using theinstrument without the instrument housing obstructing the eyes of thesubject.
 16. The instrument according to claim 15, wherein a ratio ofthe length of the instrument housing to the width of the instrumenthousing is between approximately 2 to 1 and approximately 12 to
 1. 17. Amethod for measuring near point of convergence (NPC) and/or near pointof accommodation (NPA) of a subject, the method comprising the steps of:providing an instrument that includes: an instrument housing, theinstrument housing including a front surface and a rear surface disposedopposite to the front surface, the instrument housing having a lengthand a width, the width of the instrument housing being less than thelength of the instrument housing so as to enable a user of theinstrument to view the eyes of a subject while the subject is beingtested using the instrument; at least one visual target disposed on orin the front surface of the instrument housing, the at least one visualtarget viewable by the subject when the subject is facing the frontsurface of the instrument; a distance measuring device disposed on or inthe front surface of the instrument housing, the distance measuringdevice configured to emit one or more output signals that arerepresentative of a distance between a measurement reference point ofthe instrument and a body surface of the subject spaced apart from themeasurement reference point of the instrument; a processing devicedisposed within the instrument housing, the processing deviceoperatively coupled to the distance measuring device, the processingdevice configured to receive the one or more output signals that areoutput by the distance measuring device and to calculate a plurality ofdistances between the measurement reference point of the instrument andthe body surface of the subject spaced apart from the measurementreference point of the instrument using the one or more output signals;and a visual display device operatively coupled to the processingdevice, the visual display device configured to display the plurality ofdistances calculated by the processing device to the user of theinstrument for at least two vision test measurement parameters of thesubject, the at least two vision test measurement parameters selectedfrom the group consisting of near point of convergence (NPC), near pointof convergence recovery (NPCr), near point of accommodation (NPA), andnear point of accommodation recovery (NPAr); wherein the instrument isin the form of a handheld instrument, and the user of the instrument isconfigured to hold the instrument housing during the use of theinstrument; displaying, by using the instrument, the at least one visualtarget to the subject so that the subject is able maintain his or hergaze on the at least one visual target while the user of the instrumentobserves the eyes of the subject; determining and recording, by usingthe instrument, the plurality of distances for the at least two visiontest measurement parameters of the subject; and displaying the pluralityof distances calculated by the processing device to the user on thevisual display device for the at least two vision test measurementparameters of the subject.
 18. The method according to claim 17, whereinthe instrument further comprises a camera disposed on or in the frontsurface of the instrument housing, the camera configured to capture apupil image of the subject while the subject is being tested using theinstrument, the camera being operatively coupled to the processingdevice; and wherein the method further comprises the step of:determining, by using the processing device, a pupil size of the subjectfrom the pupil image of the subject captured by the camera while thesubject is being tested using the instrument.
 19. The instrumentaccording to claim 1, wherein the length of the instrument housingextends in a vertical direction from a top surface of the instrumenthousing to a bottom surface of the instrument housing, and wherein thewidth of the instrument housing extends in a horizontal direction from afirst side of the instrument housing to a second side of the instrumenthousing.
 20. The instrument according to claim 15, wherein the length ofthe instrument housing extends in a vertical direction from a topsurface of the instrument housing to a bottom surface of the instrumenthousing, and wherein the width of the instrument housing extends in ahorizontal direction from a first side of the instrument housing to asecond side of the instrument housing.